1. Field of the Invention
The invention relates to a radial piston pump for generating high fuel pressure in fuel injection systems of internal combustion engines, in particular in a common rail injection system, having a driveshaft, supported in a housing, that has an eccentrically embodied shaft portion which cooperates with preferably a plurality of pistons capable of reciprocating radially, relative to the driveshaft, in a respective element bore, in order to aspirate fuel and subject it to high pressure in a high-pressure region.
2. Description of the Prior Art
A radial piston pump of the generic type described above is known from German Patent Disclosure DE 198 47 044 A1. In the known radial piston pump, an annular groove which communicates with a plurality of axially disposed grooves or channels is made in the outer jacket face of the pistons in the circumferential direction. The macroscopic channels serve to orient the pistons “hydraulically”, each in the associated element bore.
The running paths of the pistons and of the element bores must on the one hand be very smooth and have a uniform surface. On the other hand, a certain quantity of the medium to be compressed should adhere as lubricant to the surfaces, which dictates a certain surface roughness. This roughness subtracts from the load-bearing portion of the surface; that is, the full jacket face of the pistons and of the element bores cannot be effectively utilized as a running path. The surface roughness also limits the accuracy of shape and dimension to be attained. This limitation means that certain minimum plays cannot be undershot, which in turn lowers the efficiency of the radial piston pump. This effect is all the more pronounced, the higher the pressure in the radial piston pump becomes.
It is the object of the invention to increase the efficiency and lengthen the service life of the known radial piston pump.